Warning. Both the ghc and testsuite repositories tickle a case-sensitivity bug in darcs, so on Windows (only) you can't do a full darcs get for ghc or testsuite. Instead, either start with a tarball of the repository gotten from somewhere else, or do darcs get --partial. (The repository itself can't be fixed to avoid the bug, without messing up its history.)

The following repositories are the "GHC boot" libraries, i.e. the set of libraries that are necessary to build GHC. They populate the libraries/ directory of a GHC tree:

Branches

Note: only the ghc repository and the core libraries were branched for 6.8, the
extralibs packages are not found under ghc-6.8. The darcs-all script knows
where to get everything, so you don't have to worry about this, just follow the
instructions in Building/GettingTheSources.

6.6 Branch

Prepend ghc-6.6 to the name of the repository to get the 6.6 branch. For example,
the 6.6 ghc repository is at ​http://darcs.haskell.org/ghc-6.6/ghc. (Some? all? of) these
are partial repositories, so you may need to use the --partial option to darcs to get them.

Note: only the main repositories and the core libraries were branched for 6.6, the
extralibs packages are not found under ghc-6.6. The darcs-all script knows
where to get everything, so you don't have to worry about this, just follow the
instructions in Building/GettingTheSources.